A Method for Identifying Issues and Factions from Legislative Votes

Roll-call votes are being used increasingly to throw light on various aspects of the legislative process. As long as these votes are neither simply unanimous nor cast purely on party lines, they contain information that can often be rendered more intelligible by the simplification or condensation of many votes into fewer variables or dimensions. The researcher interested in a particular legislative decision can thus profit by seeing whether it exemplifies a more general and repeated type of occurrence. The techniques of analysis used in studying legislative votes are broadly applicable to collegial bodies of many sorts, including municipal, state, and national legislative bodies; party congresses and conventions; the U.S. Supreme Court; and the United Nations General Assembly.Two major questions have been asked which lead to the search for different kinds of simplifying variables in this analysis. One concerns the issues that divide a given group of legislators at a given time, i.e., what general matters are being argued about? The second concerns the subgroups of legislators within the group selected for study: what are the blocs, factions, cliques, and the like, whose more persistent existence is reflected by the division on a given vote?